Dielectric behavior and charge ordering in NaV2O5

We report the dielectric function of NaV2O5 single crystals in the gigahert z range as a function of the temperature. Well-defined dielectric anomalies are observed along all directions at the phase transition around 33 K on b oth the real and imaginary parts. Although the most anomalous behavior is s een along the two-leg ladders (b axis), the largest anomaly is obtained alo ng the rungs (a axis). These results are discussed in relation with the zig zag structure of a charge ordering model that has been suggested to explain the phase transition and the physic al properties below 33 K. [S0163-1829( 99)01934-7].